Throughout the early history of railroad locomotives both steam and diesel powered, there was relatively little use of engine exhaust silencers or mufflers, especially in so-called road locomotives. There was some use of mufflers on special locomotives for use in mines and other enclosed applications and spark arresting devices not especially intended for sound reduction have been extensively applied in the past.
With the advent of turbocharging of diesel powered locomotives, it was observed that directing the exhaust gases through the turbine had the effect of reducing the transmitted sound levels of certain frequencies of exhaust noise so that the exhaust from turbocharged locomotives appeared to be quieter than that from naturally aspirated locomotives. More recently however, the desire for further reductions in artifically produced noise in the environment has lead to the availability of exhaust silencing devices for both turbocharged and naturally aspirated locomotives designed for domestic use.
There is currently available an exhaust silencer designed for use with turbocharged diesel powered domestic road-type locomotives having a single elongated exhaust outlet, opening upwardly from the turbine. This silencer includes a dual bend offset outlet conduit, defining a passage that provides broadband sound reduction in the medium and high frequency range, combined with a large tank-like chamber surrounding the lower portion of the outlet conduit and connected thereto by perforations through the conduit wall, so as to provide sound reduction in the lower frequency ranges.
Recently, it has been desired to provide an exhaust silencer of similar effectiveness for turbocharged diesel-powered export model locomotives sold for overseas use. However, because of the lower exterior height of the export model locomotives, designed to meet the lower clearance requirement of many overseas railways, the space available within the engine hood section of the locomotive carbody of the export locomotives is not adequate to permit application of the previously designed domestic locomotive exhaust silencer arrangement.